National, state, and local tree news

A City Prepares for a Warm Long-Term Forecast

By Leslie Kaufman
Chicago, IL (May 22, 2011)- The windy city is preparing for a heat wave– a permanent one. Climate scientists have told city planners that based on current trends, Chicago will feel more like Baton Rouge than a Northern metropolis before the end of this century. Chicago is getting ready for a wetter, steamier future. Public alleyways are being repaved with materials that are permeable to water. The white oak, the state tree of Illinois, has been banned from city planting lists, and swamp oaks and sweet gum trees from the South have been given new priority.

“Cities adapt or they go away,” said Aaron N. Durnbaugh, deputy commissioner of Chicago’s Department of Environment. “Climate change is happening in both real and dramatic ways, but also in slow, pervasive ways. We can handle it, but we do need to acknowledge it. We are on a 50-year cycle, but we need to get going.“
The precise consequences of the increase of man-made greenhouse gases in the atmosphere are hard to determine, but scientists are predicting significant sea level rise; more extreme weather events like storms, tornadoes and blizzards; and, of course, much more heat. New York City, which is doing its own adaptation planning, is worried about flooding from the rising ocean. The Navy has a task force on climate change that says it should be preparing to police the equivalent of an extra sea as the Arctic ice melts.
Climatologists took into account a century’s worth of historical observations of daily temperatures and precipitation from 15 Chicago-area weather stations as well as the effect of Lake Michigan in moderating extreme heat and cold to come up with a range of possibilities based on a higher and lower range of worldwide carbon emissions. The forecasts, while not out of line with global predictions, shocked city planners. If world carbon emissions continued apace, the scientists said, Chicago would have summers like the Deep South, with as many as 72 days over 90 degrees before the end of the century. For most of the 20th century, the city averaged fewer than 15.
Updating Infrastructure
The city’s 13,000 concrete alleyways were originally built without drainage and are a nightmare every time it rains. Storm water pours off the hard surfaces and routinely floods basements and renders low-lying roads and underpasses unusable. As the region warms, Chicago is expecting more frequent and extreme storms. The bike lanes and parking spaces being added along the street are covered with permeable pavers, a weave of pavement that allows 80 percent of rainwater to filter through it to the ground below. Already 150 alleyways have been remade in this way.
Reconsidering the Trees
Trees improve air quality by absorbing carbon dioxide, and their leaves can keep 20 percent of an average rain from hitting the pavement. The problem is that for trees to reach their expected lifespan — up to 90 years — they have to be able to endure hotter conditions. Chicago has already changed from one growing zone to another in the last 30 years, and it expects to change several times again by 2070.
Knowing this, planners asked experts at the city’s botanical garden and Morton Arboretum to evaluate their planting list. They were told to remove six of the most common tree species. So Chicago is turning to swamp white oaks and bald cypress. It is like the rest of adaptation strategy, Ms. Malec-McKenna explains: “A constant ongoing process to make sure we are as resilient as we can be in facing the future.“Related Resources:New York Times- A City Prepares for a Warm Long-Term Forecast The Morton Arboretum